Magnetic record medium having permanent record pattern and information processing system using said medium

ABSTRACT

A magnetic record medium having a magnetic recording layer containing a uniformly dispersed magnetizable material having magnetic anisotropy, such as gamma-Fe2O3. The magnetizable material is predominantly physically aligned parallel to an intended direction of movement of the medium, and is physically aligned in a direction transverse to the intended direction at a plurality of selected locations spaced along a track extending in the intended direction to provide a series of spaced, magnetically detectable permanent position/clocking marks. The medium is used in information processing systems providing automatic positioning of predetermined portions of the medium, and automatic positioning and timing of recorded data on the medium.

United States Patent Miklos et al.

Minnesota Mining and Manufacturing Company, St Paul,

[73] Assignee:

1451 Feb. 4, 1975 3,200,207 0 1005 Reillcrcl =11. ..170/|00'.2s

3,404,392 10/1968 Sordcllo 179/1002 S 3,665,118 5/1972 Cooper, .Ir179/1002 S [57] ABSTRACT A magnetic record medium having a magneticrecord- Miching layer containing a uniformly dispersed magnetizablematerial having magnetic anisotropy. such as [22] Flled' May 1973gamma-M 0 The magnetizable material is predomi- PP 356,605 nantlyphysically aligned parallel to an intended direction of movement of themedium, and is physically 52 0.5. cr. 360/131, 360/51 aligned in a ftransverse W intended [51] Gllb 5/74 W"? l w efieeiiee 1 2 [58] Fieldofsearch' 179/1002 A, 100.2 5; track extendlng 1n the intended directionto provide a 100/2 MD; 340/ 174.1 A; 360/ 134, ser es of spaced,magnetically detectable permanent 360/5 6 131 27 5146 positron/clockingmarks. The medium 15 used in information processing systems providingautomatic posi- [56] References Cited tioning of predetermineddportionsoff the nziecliiudm, and automatic POSIIIOI'IIng an tlmll'lg O I'CCOI' eata OIl UNITED STATES PATENTS the medium. 2,923,589 2/1960 Curtis340/l74.1 A 3,114,010 12/1963 Wolf et a1 179/1002 s 13 Chums 5 Drawms sCLOCK PULSf 0km: S/GNAL MAGNET/2M6 PROCESSOR PROIESSUE .SOU/PCZ PATENTEUEB 4191s SHEET 10F 2 v 50 FIG. 3

PATENTED FEB 4 I975 SHEET 2 OF 2 REFERENCE SIGNAL GENERATOR SIGNALPROCESSOR MAGn/[T/Z/NG 60 sourecz MA GIVE T/Z/NG 50 UEC/E DATA .S/GW/QLPROZESSOP CLOCK PULS PROCESSOR MAGNETIC RECORD MEDIUM HAVING PERMANENTRECORD PATTERN AND INFORMATION PROCESSING SYSTEM USING SAID MEDIUM CROSSREFERENCE TO RELATED APPLICATION This application is related to thecopending application of the present inventors, entitled, METHOD OFMAKING A MAGNETIC RECORD MEDIUM FOR USE IN INFORMATION PROCESSINGSYSTEMS. Ser. No. 356,604 to the application of Richard E. Fayling,entitled, MAGNETIC RECORD MEDIUM AU- THENTICATION SYSTEM, Ser. No.356,602 and to the application of Richard E. Fayling and Douglas D.Campbell entitled, MAGNETIC SECURITY DOCU- MENT AND METHOD FOR MAKINGSAME, Ser. No. 356,603 all of which applications were filed on May 2,I973 and are assigned to the same assignee as this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionpertains to magnetic record media and especially to techniques forinterrogating fixed information from such media.

2. Description of the Prior Art The expanded use of magnetic recordmedia for processing large amounts of magnetically encoded data hascreated a great need for providing record media with permanent, fixedinformation patterns to be used for indexing, positioning or timingpurposes. Information processing systems using such media includetransducers acting on the permanent patterns in order to produce signalsrepresenting the fixed information,

thereby enabling the location of particular portions of the media andthe activation of other control functions as desired.

It is known to provide permanent fixed information patterns in magneticrecording media by affixing conductive metal foil strips at appropriatelocations to be sensed by electrical contacts, photocells and the like.Similarly, the media may be perforated at desired locations, whereby theperforations are mechanically or optically sensed.

Magnetic record media which are disclosed in U.S. Pat. Nos. 3,566,356,3,052,567, 3,219,353 and 3,328,195, contain multiple layers orcomposites of magnetizable material which are designed to respond todifferent types of magnetic fields, or to provide easily erasedinformation on one layer and more difficulty erased information onanother layer. A particular fixed information pattern, such as positionor clocking marks, can be recorded in that portion of the media fromwhich information is more difficultly erased and thereafter sensed toprovide signals representing the fixed information as is shown in U.S.Pat. No. 3,404,392 However, such patterns can be inadvertently erased oraltered in the process ofconventionally recording other data on themedia.

Standard techniques of making magnetic recording media having physicallyaligned particles include preparing a dispersion of the magneticparticles, knife coating the dispersion onto a smooth substrate andsubjecting the resultant coating to a quietizer field to therebyphysically align the particles along the direction ofthe field.

SUMMARY OF THE INVENTION The present invention provides an improvedrecord medium ofthe general type described in the copending 5 patentapplications cross-referenced hereinabove.

Magnetic record media typically contain a layer comprising magnetizablematerial, such as a uniform dispersion of magnetically anisotropicparticles in a nonmagnetic binder. in which the magnetizable material ispredominantly physically aligned parallel to an intended direction ofmovement of the medium. In this invention, the magnetizable material ata plurality of selected locations spaced along a track extending in theintended direction ofmovement ofthe medium is physically aligned in adirection transverse thereto to provide magnetically detectablepermanent position or clocking marks. In a preferred embodiment, theselected locations are uniformly spaced along the track to provide aseries of uniformly spaced marks.

The magnetizable material preferably comprises anisotropic particleshaving associated therewith an easy direction of magnetization. Thus,when the particles are physically aligned and a magnetic field isapplied along the easy direction of magnetization, a different,

higher level of remanent magnetization is produced than is produced whenthe same field is impressed along a direction other than the easydirection. Such variations in the remanence allows magnetic detection ofthe selected locations.

The present invention also provides an information processing systemincluding a record medium such as that described above, in which themagnetizable material positioned at selected locations along a trackextending in the intended direction of movement of the medium isphysically aligned in a direction transverse thereto to provide a seriesof magnetically detectable permanent position/clocking marks. Asubstantially unidirectional magnetic field is applied along the trackto differently magnetize the magnetizable material depending upon thedirection of physical alignment thereof. The magnetization of thedifferently magnetized material along the track is sensed to providesignal pulses representative of each of the selected locations. Therepresentative signal pulses are processed to locate predeterminedportions of the record medium. In one preferred embodiment therepresentative signal pulses are counted and compared with a referencesignal to locate a predetermined portion of the record medium. Theselected locations cannot be inadvertently erased, and thereby enhancethe reliability and convenience of systems which reuse such magneticmedia and which need a reliable and inexpensive way to locate and keeptrack of particular recorded information such as may be recordedthereon.

In another preferred embodiment of the information processing system thedifferently physically aligned selected locations are uniformly spacedalong the track to provide a series of uniformly spaced magneticallydetectable permanent clocking marks corresponding to a series of databit locations. The medium is moved along a track and a magnetic field isapplied to differently magnetize the material as described hereinabove.The magnetization of the differently magnetized materials along thetrack is sensed to produce a signal pulse representative of each of theselected locations. The representative signal pulses are then convertedinto a series of uniformly spaced shaped clocking pulses correspondingto series of data bit locations to enable recording/reproduction of databits in/from each data bit location.

Digital recording systems typically require a time reference which isconventionally recorded along with digital data. In the presentembodiment the clocking pulses provide a time reference which isindependent of any conventionally magnetically recorded data and whichis permanent and cannot be inadvertently erased or destroyed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a three-dimensional view of aportion of a magnetic record medium according to the present inventionhaving a magnetic recording layer containing a uniform dispersionofmagnetizable material in which selected locations within the layer arephysically aligned differently from the material in the remainder of thelayer;

FIG. 2 is an enlarged cross-sectional view of a segment of the recordingmedium shown in FIG. 1;

FIG. 3 is a three-dimensional view of a portion of a magnetic recordmedium according to the present invention having predetermined recordingregions and having selected locations of differently physically alignedmaterial corresponding to each of the predetermined regions;

FIG. 4 is a combined three-dimensional and schematic view of aninformation processing system according to the present invention forlocating predetermined portions of a magnetic record medium;

FIG. 5 is a combined three-dimensional and schematic view of aninformation processing system for providing clock pulses correspondingto locations whereat binary data may be magnetically recorded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a segment ofamagnetic record medium which comprises a thin sheet-like web backing 12upon which is coated a magnetic recording layer 14 containing auniformly dispersed magnetizable material having magnetic anisotropy.Such amateriaipreferably consists of anisotropic particles ofgamma-Fe Osuch as are commonly usedin magnetic recording media. An outerprotective layer 15 may be affixed to the recording layer 14 as desired.By uniformly dispersed it is herein meant that the particle density,i.e., the number of particles per unit area, is approximately constantthroughout the layer, even though the particles may be differentlyphysically aligned at various locations. The magnetizable material ispredominantly physically aligned parallel to a long dimension of themedium along which the medium is intended to travel during use. Such adirection of physical alignment is shown by the double-headed arrow 22,and corresponds with the physical alignment of magnetizable particles inconventional magnetic recording media. The magnetizable material at aplurality of selected locations 16 is differently physically alignedwith respect to the physical alignment of the particles in the remainderof the layer 14, and is preferably aligned in a direction transversethereto to provide a series of spaced, magnetically detectable,permanent position/clocking marks, which are desirably used inconjunction with data such as may be magnetically recorded in theremainder of the medium I8 such as along a track 21.

Anisotropic particles such as gamma-H 0 are readily magnetized in eitherdirection parallel to their easy direction of magnetization. Thus, whensuch particles are physically aligned and are magnetized with a givenapplied field along the easy direction of magnetization, a higher levelof remanent magnetization is retained than is retained should theapplied magnetic field be along a direction other than the easydirection. The variations in the remanent magnetization may be sensed todetect the selected locations 16.

.FIG. 2 is an enlarged cross-section ofa portion ofanother magneticrecording medium 24 comprising a thin sheet-like web backing 26 uponwhich is coated a magnetic recording layer 28 such as described above.An optional outer protective layer 29 may be affixed to the magneticrecording layer 28. The layer 28 contains acicular particles 30 ofgamma-Fe o which are uniformly dispersed within a flexible binder 31.The particles are shown further enlarged for graphic clarity. The layer28 has background portions 32 and 34 within which the particles areuniformly physically aligned in one direction parallel to both thesurface of the medium 24 and to the long dimension along which thedocument is intended to move. Portion 36 represents a selected locationat which the particles 30 are further physically aligned, still parallelto the surface of the medium 24, but also normal to the physicallyaligned particles within the background portion 32 and 34. Thedelineation between the portions 32 and 34 and the selected location 36is shown for clarity as an abrupt transition in the direction ofalignment ofphysical the particles. Due to the normal divergence of themagnet flux, such a transition will generally extend over a distancedictated by the characteristics of the aligning magnetic field.

Methods for making such magnetic media are described and claimed in theabove cross-referenced patent applications by the present inventors andby Richard E. Fayling and Douglas D. Campbell, the disclosures of whichare incorporated herein by reference. The magnetic recording layers usedin the magnetic recording media of the present invention mayconveniently be a stripe of conventional magnetic recording media formedor affixed to a sheet-like web backing, such as a 1 mil. (0.025 mm.)polyethylene terephthalate sheet, and are typically formed of a mixtureof the magnetizable material, a nonmagnetic flexible organic binder anda suitable solvent, which mixture is coated untothe web backing andsubjected to appropriate magnetic fields to physically align theparticles. In a typical case. such a coating comprises a uniformdispersion of 65wt. percent gamma-Fe O acicular particles (typically 500micrometers long and micrometers diameter) and 35 wt. percentthermoplastic polyurethane binder together with a suitable solvent. Thethickness of such a coating is typically controlled to be 0.004 inches(0.10 mm. Other formulations, substrate and coatingthicknesses may besimilarly employed consistent with known magnetic recording mediaformulations.

FIG. 3 is a three-dimensional view of a portion of a magnetic recordmedium 40 of the present invention, which comprises a substrate 42 and amagnetic recording layer 44 containing uniformly dispersed magneticallyanisotropic particles of gamma-Fe O The layer 44 has data magneticallyrecorded at a plurality of predetermined recording regions 46 and 48.Such inform ation is conveniently recorded along a number of tracksextending in the intended direction of movement of the medium, i.e.,parallel to the long dimension 56 of the medium 40, within which tracksthe particles are predominantly physically aligned parallel to theintended direction of movement. Associated with each recording region 46and 48 is a selected location 50 and 52, positioned along a controltrack 54 extending in the intended direction movement of the medium. Themagnetizable material within the selected locations 50 and 52 isphysically aligned normal to the control track 54.

FIG. 4 shows an embodiment of the present invention for determining thelocation of the predetermined recording regions 46 and 48 of the recordmedium 40. In this embodiment, the magnetic record medium 40 describedhereinabove is traversed in the direction indicated by the arrow 49 by aconventional capstan 51 and roller 53 coupled to a drive mechanism (notshown) parallel to the track 54. A magnetic field generating device 58,such as a conventional magnetic recording head, when energized by themagnetizing power source 60, produces a substantially unidirectionalmagnetic field having a major field component which is applied in therecording layer 44 parallel to the long dimension 56 along the track 54.Alternatively, the field generating device 58 may be an appropriatelyshaped and posi tioned permanent magnet. As the record medium passes thefield generating device 58, all portions of the track 54 are subjectedto a constant intensity magnetic field to differently magnetize theparticles depending upon the physical alignment thereof along the track.This produces varying states of remanence in the particles such that asthe record medium 40 thereafter passes adjacent the sensor device 62 thevarying states of remanence are sensed to provide a signalrepresentative ofthe selected locations 50, 52. The sensor device 62 ispreferably a conventional magnetic recording playback head. However,Hall probes or other magnetic field sensors may likewise be used. Thesignal is then processed in a signal processor unit 64 which convertsthe sensed signals to a form compatible with standardized informationprocessing formats. When the sensed signals are counted from a knownlocation on the record medium 40 such as the beginning or leading edgethereof along the direction of travel, and are compared with a referencesignal such as produced by a reference signal generator 66, the specificlocation of any given one of the selected locations may be determined.The two signals are readily compared by conventional electronicprocessing circuits such as contained within a signal comparator unit68, which produces an output signal to be coupled to indicator devices,control mechanisms-and the like.

FIG. 5 shows an embodiment of the present invention for providngpermanent clocking pulses associated with magnetically recorded data ona magnetic record medium such as described hereinabove. The magneticrecord medium 70 contains selected locations 72 which are uniformlyspaced along a track 74 extending in a direction parallel to an edge 76of the record medium 70, which direction is also parallel to an intendeddirection of movement of the medium 70. As discussed hereinabove, themagnetic record medium 70 comprises a substrate 77 and a magneticrecording layer 78 within which magnetizable material is predominantlyphysically aligned parallel to the intended direction of movement suchas shown by the double-headed arrows 80,

and wherein the magnetizable material within the selected locations 72is predominantly physically aligned normal to the intended direction ofmovement. When the medium is moved at a uniform speed along a pathparallel to the track 74, a magnetic field. produced by the magnetizingdevice 82 in response to energization by the magnetizing source 84, isapplied in the recording layer 78 along the track 74, to cause theselected locations 72 to become differently magnetized from theremainder of the recording layer 78 along the track 74, in the samemanner as described hereinabove. A magnetic sensor device 86, such as aconventional magnetic recording playback head is also positioned alongthe track 74 to sense the different magnetization and thereby generate atrain of uniformly spaced signal pulses, which are subsequentlyprocessed and shaped in clock pulse processor unit 88. The magneticrecord medium 70 also contains a number of recording tracks 90, 92, and94, which extend parallel to the track 74, within which are a series ofdata bit locations, each location having a selected location 72corresponding thereto. Each clock pulse thereby provides a signalindication, enabling recording and reproduction ofa data bit from eachdata bit location by means of transducers 98. The clock pulses areconverted in a clock pulse processor unit 88 into a series of uniformlyspaced shaped clocking pulses which are transmitted to a data signalprocessor unit 96 which enables recording and reproduction of the databits in the corresponding data bit locations.

What is claimed is:

1. In a magnetic recording medium comprising a backing and a layerthereon having a smooth outer surface, which layer comprises uniformlydispersed magmovement of the medium being physicaly aligned in adirection transverse thereto to provide a series of spaced magneticallydetectable permanent position/- clocking marks.

2. A magnetic recording medium according to claim 1 wherein said layercomprises magnetizable particles uniformly dispersed in a nonmagneticbinder.

3. A magnetic recording medium according to claim 2, wherein themagnetizable particles are acicular gamma-Fe O 4. A magnetic recordingmedium according to claim 2, wherein the predominant physical alignmentin said one direction is parallel to the plane of the medium and themagnetizable particles within each of said selected locations arephysically aligned parallel to the plane of the medium and perpendicularto said one direction.

5. In a magnetic recording medium comprising a backing and a layerthereon having a smooth outer surface, which layer comprises uniformlydispersed magnetizable material having magnetic anisotropy whichmagnetizable material is predominantly. physically aligned parallel toan intended direction of movement. wherein the improvement comprises themagnetizable material at a plurality of selected locations uniformlyspaced along a track extending in said intended direction of movement ofthe medium being physically aligned in a direction transverse thereto toprovide a series of uniformly spaced magnetically detectable permanentposition/clocking marks.

6. A magnetic recording medium according to claim wherein the layercomprises magnetizable particles uniformly dispersed in a nonmagneticbinder.

7. A magnetic recording medium according to claim 6, wherein themagnetizable particles are acicular gamma-Fe O 8. A magnetic recordingmedium according to claim 6, wherein the predominant physical alignmentin said one direction is parallel to the plane of the medium and themagnetizable particles within each of said selected locations arephysically aligned parallel to the plane of the medium and perpendicularto said one direction. I 9. ln a magnetic recording medium comprising abacking and a layer thereon having a smooth outer surface, which layercomprises uniformly dispersed magnetizable material having magneticanisotropy, which magnetizable material is predominantly physicallyaligned parallel to an intended direction of movement, and wherein saidlayer has data magnetically recorded at a plurality of predeterminedrecording regions, wherein the improvement comprises the magnetizablematerial at a plurality of selected locations along a control trackextending in said intended direction of movement of the medium andspatially correlated with the predetermined recording regions beingdifferently physically aligned from the alignment of the magnetizableparticles in the remainder of the layer to provide magneticallydetectable permanent position marks for indicating the positions of thepredetermined recording regions.

10. In a magnetic recording medium according to claim 9, wherein saidpredetermined recording regions are uniformly spaced along at least onerecording track parallel to said one direction, said recording regionsforming data bit locations for magnetically recorded binary data,wherein said selected locations are uniformly spaced along said controltrack to provide a series of uniformly spaced magnetically detectablepermanent clocking marks corresponding to the series of data bitlocations for providing signal indications for enabling reproduction ofa data bit from each data bit location of. said at least one recordingtrack.

11. An information processing system for determin ing the location ofpredetermined portions of a record medium, which system comprises:

a magnetic recording medium comprising a backing and a layer thereonhaving a smooth outer surface,

which layer comprises uniformly dispersed magnetizable material havingmagnetic anisotropy, which magnetizable material is predominantlyphysically aligned parallel to said intended direction of movement, andwherein the magnetizable material at a plurality of selected locationsspaced along a track extending in said intended direction of movement ofthe medium is physically aligned in a direction transverse thereto toprovide a series of spaced magnetically detectable permanentposition/clocking marks;

means for moving said medium in said direction parallel to said track;

means for applying a substantially constant intensity unidirectionalmagnetic field along said track to differently magnetize saidmagnetizable material depending upon the direction of physical alignmentthereof; and

means for sensing the magnetization along said track when sid recordmedium is moved in a direction parallel to said track to produce signalpulses representative of said selected locations; and

means for processing said representative signal pulses to locatepredetermined portions of said record medium.

12. A system according to claim 11, wherein the magnetizable materialwithin each of said selected locations is physically aligned parallel tothe plane of the medium and perpendicular to said one direction, wherebythe applied magnetic field magnetizes the magnetizable material otherthan at said selected locations along said track to a first remanentstate and mag netizes the magnetizable material within the selectedlocations along said track to a second lower remanent state.

13. An information processing system according to claim 11, forproviding clocking pulses, wherein said selected locations are uniformlyspaced along said track to provide a series of uniformly spacedmagnetically detectable permanent clocking marks corresponding to aseries of data bit locations, and wherein said signal processing meanscomprises means coupled to said sensing means for converting saidrepresentative signal pulses into a series of uniformly spaced clockingpulses corresponding to the series of data bit locations to enablerecording/reproduction of data bits in/from each said data bit location.

1. In a magnetic recording medium comprising a backing and a layerthereon having a smooth outer surface, which layer comprises uniformlydispersEd magnetizable material having magnetic anisotropy whichmagnetizable material is predominantly physically aligned parallel to anintended direction of movement, wherein the improvement comprises themagnetizable material at a plurality of selected locations spaced alonga track extending in said intended direction of movement of the mediumbeing physicaly aligned in a direction transverse thereto to provide aseries of spaced magnetically detectable permanent position/clockingmarks.
 2. A magnetic recording medium according to claim 1 wherein saidlayer comprises magnetizable particles uniformly dispersed in anonmagnetic binder.
 3. A magnetic recording medium according to claim 2,wherein the magnetizable particles are acicular gamma-Fe2O3.
 4. Amagnetic recording medium according to claim 2, wherein the predominantphysical alignment in said one direction is parallel to the plane of themedium and the magnetizable particles within each of said selectedlocations are physically aligned parallel to the plane of the medium andperpendicular to said one direction.
 5. In a magnetic recording mediumcomprising a backing and a layer thereon having a smooth outer surface,which layer comprises uniformly dispersed magnetizable material havingmagnetic anisotropy which magnetizable material is predominantlyphysically aligned parallel to an intended direction of movement,wherein the improvement comprises the magnetizable material at aplurality of selected locations uniformly spaced along a track extendingin said intended direction of movement of the medium being physicallyaligned in a direction transverse thereto to provide a series ofuniformly spaced magnetically detectable permanent position/clockingmarks.
 6. A magnetic recording medium according to claim 5 wherein thelayer comprises magnetizable particles uniformly dispersed in anonmagnetic binder.
 7. A magnetic recording medium according to claim 6,wherein the magnetizable particles are acicular gamma-Fe2O3.
 8. Amagnetic recording medium according to claim 6, wherein the predominantphysical alignment in said one direction is parallel to the plane of themedium and the magnetizable particles within each of said selectedlocations are physically aligned parallel to the plane of the medium andperpendicular to said one direction.
 9. In a magnetic recording mediumcomprising a backing and a layer thereon having a smooth outer surface,which layer comprises uniformly dispersed magnetizable material havingmagnetic anisotropy, which magnetizable material is predominantlyphysically aligned parallel to an intended direction of movement, andwherein said layer has data magnetically recorded at a plurality ofpredetermined recording regions, wherein the improvement comprises themagnetizable material at a plurality of selected locations along acontrol track extending in said intended direction of movement of themedium and spatially correlated with the predetermined recording regionsbeing differently physically aligned from the alignment of themagnetizable particles in the remainder of the layer to providemagnetically detectable permanent position marks for indicating thepositions of the predetermined recording regions.
 10. In a magneticrecording medium according to claim 9, wherein said predeterminedrecording regions are uniformly spaced along at least one recordingtrack parallel to said one direction, said recording regions formingdata bit locations for magnetically recorded binary data, wherein saidselected locations are uniformly spaced along said control track toprovide a series of uniformly spaced magnetically detectable permanentclocking marks corresponding to the series of data bit locations forproviding signal indications for enabling reproduction of a data bitfrom each data bit location of said at least one recording track.
 11. Aninformation processing system for determining the location ofpredetermined portions of a record medium, which system comprises: amagnetic recording medium comprising a backing and a layer thereonhaving a smooth outer surface, which layer comprises uniformly dispersedmagnetizable material having magnetic anisotropy, which magnetizablematerial is predominantly physically aligned parallel to said intendeddirection of movement, and wherein the magnetizable material at aplurality of selected locations spaced along a track extending in saidintended direction of movement of the medium is physically aligned in adirection transverse thereto to provide a series of spaced magneticallydetectable permanent position/clocking marks; means for moving saidmedium in said direction parallel to said track; means for applying asubstantially constant intensity unidirectional magnetic field alongsaid track to differently magnetize said magnetizable material dependingupon the direction of physical alignment thereof; and means for sensingthe magnetization along said track when sid record medium is moved in adirection parallel to said track to produce signal pulses representativeof said selected locations; and means for processing said representativesignal pulses to locate predetermined portions of said record medium.12. A system according to claim 11, wherein the magnetizable materialwithin each of said selected locations is physically aligned parallel tothe plane of the medium and perpendicular to said one direction, wherebythe applied magnetic field magnetizes the magnetizable material otherthan at said selected locations along said track to a first remanentstate and magnetizes the magnetizable material within the selectedlocations along said track to a second lower remanent state.
 13. Aninformation processing system according to claim 11, for providingclocking pulses, wherein said selected locations are uniformly spacedalong said track to provide a series of uniformly spaced magneticallydetectable permanent clocking marks corresponding to a series of databit locations, and wherein said signal processing means comprises meanscoupled to said sensing means for converting said representative signalpulses into a series of uniformly spaced clocking pulses correspondingto the series of data bit locations to enable recording/reproduction ofdata bits in/from each said data bit location.